Die for hot-pressing powdered metal



DIE FOR- HOT-PRESSING POWDERED METAL (1&1951969 R.E.R|CE 3,461,507

Filed April 26; 1967 .Zizaezztor United States Patent US. Cl. 18-47 3 Claims ABSTRACT OF THE DISCLOSURE Apparatus for forming articles by hot-pressing powdered metal comprising a die made in a plurality of sections to facilitate finishing the interior surfaces before assembly, the sections being held together with substantially uniform tightness throughout the wide range of temperatures involved in hot-pressing.

In hot-pressing powdered metal it has been proposed to make the die in two or more sections of tungsten carbide or the like and, after the interior surfaces of the sections are finished, to shrink-fit steel retaining rings around the sections to hold them in assembled relationship. However this construction has not been satisfactory. If shrink-fitted to hold the sections tightly at room temperature the rings are too loose at the high temperatures involved in hot pressing, and if properly fitted to hold the sections at the high temperatures the parts would be overstrained at room temperatures. To make the retaining rings of the same carbide material as the dies involves excessive cost.

Objects of the present invention are to make a multisection die which remains tightly closed throughout the entire range of temperatures involved in hot-pressing, which involves no overstraining, which can be manufactured easily and which does not involve excessive cost.

According to this invention the sections are held together with wire wound around the sections, the wire having a thermal expansion coeflicient closely matching that of the sections. The preferred metals are tungsten carbide for the sections and either tungsten or molybdenum for the wire. The cost of the wire is much less than that of tungsten or molybdenum rings and, as hereinafter explained, the wire can be applied more economically than rings.

For the purpose of illustration a typical embodiment is shown in the accompanying drawings in which FIG. 1 is a side view partly in section showing the preferred method of manufacture;

FIG. 2 is a view from the right of FIG. 1;

FIG. 3 is a side view of the die after the wire has been Wound but before the outer end of the Wire has been permanently anchored; and

3,461,507 Patented Aug. 19, 1969 FIG. 4 is a section on line 44 of FIG. 3 after the die is completed.

The particular embodiment chosen for the purpose of illustration comprises a cylindrical die 1 divided longitudinally into three sections as shown in FIG. 2. At the ends the die has peripheral flanges 2 and 3 to define a Winding space 4 so that when the sections are assembled together the die is like a spool. At one end the die has an axial flange 6 for the purpose of mounting the die in a lathe 7 (FIG. 1) for rotation about its axis to wind wire 8 in space 4. Mounted in radial bores 11 and 12 in the flanges 2 and 3 are pins 13 and 14 for temporarily anchoring the ends of the wire. Before winding, the end of the wire is secured to pin 13 (FIG. 1) and after the winding is completed the wire is secured to pin 14 temporarily (FIG. 3). After the winding is completed the inner end of the wire is held by the overlapping layer of layers of wire and the outer end is brazed to the die as shown at 16 in FIG. 4. After completion the end of the wire may be cut off and the pins 13 and 14 removed. During winding the wire is maintained under controlled tension so that the die is not overcompressed and so that the joints between the sections do not open in using the die.

It should be understood that the present disclosure is for the purpose of illustration only and that this invention includes all modifications and equivalents which fall Within the scope of the appended claims.

I claim:

1. For forming articles of powdered metal, apparatus comprising a die for compacting the metal, the die consisting of several sections held together by a winding of refractory metal wire having a thermal expansion coefficient closely matching that of the sections.

2. A die according to claim 1 wherein the wire is either tungsten or molybdenum.

3. A die according to claim 2 wherein said sections comprise tungsten carbide.

References Cited UNITED STATES PATENTS 3,061,877 11/1962 Custers et al.

3,067,465 12/1962 Giardini et al.

3,085,291 4/1963 Haes et al. 18-165 3,088,170 5/1963 Strong.

3,149,374 9/ 1964 Wagner.

3,213,491 10/1965 Craig.

3,309,738 3/1967 Friedman 249-164 X J. HOWARD FLINT, JR., Primary Examiner US. Cl. X.R. 

